Immersion Liquid, Exposure Apparatus, and Exposure Process

ABSTRACT

An immersion liquid is provided comprising an ion-forming component, e.g. an acid or a base, that has a relatively high vapor pressure. Also provided are lithography processes and lithography systems using the immersion liquid.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. application Ser. No.11/071,044, filed on 3 Mar. 2005, which claims the benefit of U.S.provisional application 60/651,513, filed on 10 Feb. 2005. Both priorityapplications are hereby incorporated in their entirety by reference.

FIELD

The invention relates to immersion liquids, exposure apparatus, andexposure processes.

BACKGROUND

Immersion lithography is gaining attention due to improvements incritical dimensions and/or depth of focus that it provides. However, thetechnology also faces some concerns. For instance, on the one hand anultra-pure immersion liquid may be advantageous to minimize theappearance of stains when drying areas wetted by the liquid, but on theother hand it may be desirable to include additives in the immersionliquid to influence or create desirable properties. E.g., it may bedesirable to include acid components in the immersion liquid to avoid orminimize so-called T-topping or other undesirable effects. T-topping,for instance, may occur when a resist layer on a substrate to be exposedto radiation comes into contact with the immersion liquid and componentsin the resist (e.g. photo-acid generators) diffuse or dissolve into theimmersion liquid. See also EP 1482 372 A1.

Accordingly, objectives of the invention include providing an immersionliquid comprising one or more additives yet having reduced stainingconcerns.

Also, objectives of the invention include avoiding or minimizingstreaming potential effects caused by the flow of immersion liquid(discussed in more detail infra).

SUMMARY

The invention provides immersion liquids, exposure apparatus, andexposure processes.

In an embodiment, the invention provides an immersion liquid formed by amethod comprising adding an ion-forming component to a liquid (e.g. anaqueous liquid), wherein said ion-forming component has a vapor pressuregreater than O.1 kPa, e.g. greater than water.

In an embodiment, the invention provides an immersion liquid having a pHbelow 7, said pH below 7 being at least partly caused by a componenthaving a vapor pressure greater than 0.1 kPa, e.g. greater than water.

In an embodiment, the invention provides an immersion liquid having a pHgreater than 7, said pH greater than 7 being at least partly caused by acomponent having a vapor pressure greater than 0.1 kPa, e.g. greaterthan water.

In an embodiment, the invention provides an immersion liquid having anelectric conductivity of at least 0.1 μS/cm, e.g. at least 1.3 μS/cm at25° C. ha an embodiment, the invention provides an immersion liquidhaving an electric conductivity in the range of 0.1-100 μS/cm at 25° C.,e.g. in the range of 1.3-100 μS/cm at 25° C. In an embodiment, theconductivity is at least partly caused by a component having a vaporpressure greater than 0.1 kPa, e.g. greater than water.

Also, the invention provides processes, e.g. an immersion lithographyprocess, using the immersion liquids. In an embodiment, the inventionprovides a device manufacturing process comprising exposing aphotosensitive substrate to radiation, wherein said radiation has passedthrough the immersion liquid prior to reaching said substrate.

In addition, the invention provides immersion lithography systemscomprising an immersion lithography apparatus and one or more of theimmersion liquids.

In an embodiment, the invention provides a process comprising:

(i) adding a component to a liquid, said component having a vaporpressure greater than 0.1 IcPa, e.g. greater than water;

(ii) exposing a photosensitive substrate to radiation, wherein saidradiation has passed through said aqueous liquid comprising saidcomponent prior to reaching said photosensitive substrate;

wherein said adding of said component increases the ion concentration insaid liquid.

In an embodiment, the invention provides a process comprising:

(i) adding an acid to a liquid, said acid having a vapor pressure of atleast 0.IkPa, e.g. at least 5 kPa;

(ii) exposing a photosensitive substrate to radiation, wherein saidradiation has passed through said liquid comprising said component priorto reaching said photosensitive substrate.

In an embodiment, the invention provides a process comprising:

(i) patterning a beam of radiation;

(ii) passing the patterned beam of radiation through a liquid (e.g. anaqueous liquid), said liquid comprising ions formed by a componenthaving a vapor pressure greater than 0.1 kPa, the conductivity of saidliquid being at least 0.25 μS/cm;

(iii) exposing a photosensitive substrate to the patterned beam ofradiation.

In an embodiment, the invention provides an immersion lithography systemcomprising:

(i) an immersion lithography exposure apparatus; and

(ii) an immersion liquid, e.g. an immersion having an electricconductivity in the range of 0.1-100 μS/cm at 25° C. (for instance inthe range of 1.3-100 μS/cm at 25° C.) or a carbon dioxide enrichedimmersion liquid.

In an embodiment, the invention provides a lithography apparatus havinga voltage generator capable of applying a voltage difference between afirst part of a lithography apparatus, e.g. a substrate table, and asecond part of the lithography apparatus, e.g. an immersion hood of animmersion lithography apparatus. In an embodiment, the inventionprovides a process comprising applying a voltage difference between afirst part of a lithography apparatus, e.g. the substrate table, and asecond part of the lithography apparatus, e.g. the immersion hood of animmersion lithography apparatus.

Additional objects, advantages and features of the invention are setforth in this specification, and in part will become apparent to thoseskilled in the art on examination of the following, or may be learned bypractice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents an immersion lithography system according to anembodiment of the invention.

FIG. 2 represents an embodiment of an immersion hood of an immersionlithography system according to an embodiment of the invention.

DETAILED DESCRIPTION

Preliminarily, this application at various instances refers to vaporpressures of components, ha this regard, the vapor pressure of acomponent refers to the vapor pressure of a component in its pure form(thus not in a mixture or in solution) at 20° C.

In an embodiment, the invention provides an immersion liquid. Also, theinvention provides a process using an immersion liquid, e.g. animmersion lithography process.

Immersion Liquid

In an embodiment, the immersion liquid is prepared by a processcomprising adding one or more components to a liquid, e.g. an aqueousliquid, for instance a liquid comprising, relative to the total weightof the liquid, at least 50 wt % water, such as at least 75 wt % water,at least 90 wt % water, at least 95 wt % water, at least 99 wt % water,at least 99.5 wt % water, at least 99.9 wt % water, or at least 99.99 wt% water. In an embodiment, the liquid, before adding the one or morecomponents, has an electric conductivity of less than 0.1 μS/cm (asdetermined at 25° C.). In an embodiment, the liquid is de-gassed beforeadding the one or more components. In an embodiment, the liquid ispurified before adding the one or more components. In an embodiment, theliquid is ultra-pure, de-gassed water.

In an embodiment, the component added to the liquid has a relativelyhigh vapor pressure. A high vapor pressure may assist, e.g., in avoidingstains on a substrate when immersion liquid is removed (e.g.,evaporated) from the substrate. In an embodiment, the component added tothe liquid has a vapor pressure exceeding the vapor pressure of theliquid it is added to. In an embodiment, the component added to theliquid has a vapor pressure of at least 0.1 kPa, e.g. at least 0.25 kPa,at least 0.5 kPa, at least 0.75 kPa, at least 1 kPa, at least 1.3 kPa,at least 1.5 kPa, at least 1.8 kPa, at least 2.1 kPa, or exceeding thevapor pressure of water (i.e., exceeding 2.34 kPa). In an embodiment,the component added to the liquid has a vapor pressure of at least 3.5kPa, such as at least 5 kPa, at least 1 OkPa, at least 2 OkPa, at least3 OkPa, or at least 5 OkPa. In an embodiment, the component being addedis formic acid or acetic acid. In an embodiment, the component added tothe liquid is, in its pure form at 20° C. and at 1 atmosphere pressure,a gas. In an embodiment, the component added to the liquid is carbondioxide. In an embodiment, the immersion liquid comprises, relative tothe total weight of the immersion liquid, less than 5 wt % of componentshaving a vapor pressure below 2.OkPa (e.g. below 1.5 kPa, below 1 kPa,below 0.5 kPa, below 0.25 IcPa, below 0.1 kPa, or OkPa), e.g. less than3 wt %, less than 1 wt %, less than 0.5 wt %, less than 0.25 wt %, lessthan 0.1 wt %, less than 0.05 wt %, less than 0.025 wt %, less than 0.01wt %, or less than 0.005 wt %. In an embodiment, the immersion liquidcomprising the component having a relatively high vapor pressure is, nottaking into account the main constituent of the immersion liquid (e.g.,water in an immersion liquid having water as the main constituent),essentially absent components having a vapor pressure below 2.OkPa, e.g.below 1.5 kPa, below 1 kPa, below 0.5 kPa, below 0.25 kPa, below 0.1kPa, or OkPa.

In an embodiment, the component added to the liquid promotesconductivity of the liquid, e.g. by promoting ion formation. Increasedconductivity of the immersion liquid may assist in decreasing oravoiding streaming potential concerns. Streaming potential is discussedin, e.g., the article “Streaming Potential Cells For The Study ofErosion-Corrosion Caused By Liquid Flow” by Varga and Dunne in J. Phys.D: Appl. Phys., 18 (1985), p. 21 1-220. Streaming potential may, e.g.,shorten the lifetime, for instance through corrosion or erosion, of e.g.coatings, sensors and/or (alignment) markers that come into contact withthe flow of immersion liquid (in particular substantially conductivecomponents of, e.g., coatings, sensors, and/or markers). In anembodiment, the conductivity of the liquid comprising the component isat least 0.1 μS/cm at 25° C., for instance at least 0.25 μS/cm, at least0.5 μS/cm, at least 0.75 μS/cm, at least 1 μS/cm, at least 1.3 μS/cm, atleast 1.5 μS/cm, at least 1.75 μS/cm, at least 2 μS/cm, at least 3μS/cm, at least 5 μS/cm, at least 10 μS/cm, at least 25 μS/cm, or atleast 50 μS/cm. While the above-mentioned and below-mentionedconductivities are determined at 25° C., the temperature at which theimmersion liquid is used may be different. The values referred to,however, remain the conductivities as deteπnined at 25° C.

While increased conductivity may assist in reducing or eliminating theeffect of streaming potential, it may also increase the amount ofcomponent(s) that needs to be added to the immersion liquid, which maylead to staining or bubble concerns. In an embodiment, the conductivityof the liquid comprising the component is less than 50 mS/cm at 25° C.,e.g. less than 25 mS/cm, less than 10 mS/cm, less than 5 mS/cm, lessthan 1 mS/cm, less than 500 μS/cm, less than 250 μS/cm, less than 150μS/cm, less than 75 μS/cm, less than 50 μS/cm, less than 25 μS/cm, lessthan 15 μS/cm, less than 10 μS/cm, less than 7 μS/cm, less than 4 μS/cm,or less than 2 μS/cm. In an embodiment, the conductivity of the liquidis in the range of 0.1-100 μS/cm at 25° C., e.g. 0.25-25 μS/cm, 0.4-10μS/cm, or 0.6-6 μS/cm. In one embodiment, the conductivity of theliquid, e.g. an aqueous liquid, for instance ultra-pure water, isincreased by adding salts or acids to the liquid. In an embodiment, theliquid is enriched with acetic acid, formic acid, CO₂ (CO₂ may formin/with water the ions H⁺ and HCO₃ ⁻), or NH₃ (NH₃ may form in/withwater the ions NH₄ ⁺ and OH⁻).

Also, streaming potential may be reduced or avoided by decreasing thespeed and/or turbulence of the water flow. Furthermore, while notnecessarily avoiding streaming potential itself, providing a voltagedifference between the area effected by the streaming potential (e.g.the substrate table, for instance a sensor or a sensor plate on thesubstrate table) and another area may limit or negate the undesirableeffects caused by the streaming potential. In an embodiment, theinvention provides a lithography apparatus having a voltage generatorcapable of applying a voltage difference between a first part of alithography apparatus, e.g. the substrate table, and a second part ofthe lithography apparatus, e.g. the immersion hood of an immersionlithography apparatus. In an embodiment, the invention provides aprocess comprising applying a voltage difference between a first part ofa lithography apparatus, e.g. the substrate table, and a second part ofthe lithography apparatus, e.g. the immersion hood of an immersionlithography apparatus. In an embodiment, the voltage difference is atleast 0.1V, for instance at least 0.25V, at least 0.5V, at least IV, atleast 2V, at least 3V, at least 4V, or at least 5V. In an embodiment,the voltage difference is less than 50V.

In an embodiment, the component added to the liquid is an acidiccomponent, e.g. acetic acid, formic acid, or carbon dioxide. Acidity ofthe immersion liquid may assist in maintaining the effectiveness ofresist that may come into contact with the immersion liquid, e.g. byhelping to slow down/decrease diffusion or dissolution of photo-acidgenerators, that may be present in the resist, into the immersionliquid. In an embodiment, the liquid comprising the component has a pHbelow 7, e.g. below 6.5, below 6.0, below 5.5, below 5.0, below 4.5, orbelow 4.0. In an embodiment, the pH is at least 2.0, such as at least2.5, at least 3.0, at least 3.5, at least 3.75, at least 4.0, at least4.5, at least 5.0, or at least 5.5. In an embodiment, the componentadded to the liquid is a base, e.g. ammonia (NH₃). Alkalinity of theimmersion liquid may assist in maintaining the effectiveness of resistthat may come into contact with the immersion liquid should the resistcomprise alkaline components (bases) rather than acid components thatmay leak into the immersion liquid. In an embodiment, the liquidcomprising the component has a pH above 7, e.g. above 7.5, above 8,above 8.5, above 9, above 9.5, or above 10. In an embodiment, the pH isbelow 14.

The manner of adding the (one or more) component(s) to the liquid mayvary and may depend to an extent, e.g., on the type of component beingadded (e.g., whether it is available as a gas, a solid, or a liquid). Inan embodiment, the component is added via diffusion through a membrane.For instance, the liquid may flow on one side of a membrane and thecomponent on the other side of the membrane, whereby the membrane isimpermeable to the liquid but permeable to the component, thus allowingthe component to diffuse into liquid. In an embodiment, the componentthus added is a gas, e.g. CO₂. In an embodiment, the component is addedalong with one or more inert gases, e.g. N₂. Accordingly, in anembodiment, a liquid (e.g. an aqueous liquid, for instance ultra-purewater) flows on one side of the membrane and a CO₂/N₂ mixture flows onthe other side of the membrane, allowing CO₂ and N₂ to diffuse into theliquid. Commercial examples of suitable membrane equipment include,e.g., LIQUI-CEL membrane contactors from MEMBRANA. In an embodiment, thecomponent is added to the liquid by flowing (e.g., dripping) thecomponent into the liquid (or by flowing a comparatively concentratedcomponent/liquid solution into the liquid; e.g., when the component isammonia and the liquid is water, the ammonia may be added by flowing acomparatively concentrated aqueous ammonia solution into the water). Theadding of the (one or more) component(s) may be done remote from theapparatus (the immersion liquid may be “pre-prepared”), the adding maybe done in a separate unit that is linked to the apparatus (e.g., awater purification unit for the apparatus may be adapted for adding theone or more components), or the adding may be integrated into theapparatus.

Process

The invention provides processes using the above-mentioned immersionliquids, for instance processes wherein a substrate is exposed toradiation and wherein the radiation passes through the immersion liquidbefore reaching the substrate.

In an embodiment, a process is provided comprising exposing a substrateto radiation, wherein said radiation has passed through an immersionliquid as described in the above section. In an embodiment, the processcomprises patterning a beam of radiation (e.g. with the aid of a reticleor an array of individually programmable elements), passing thepatterned beam through a projection system (e.g. an array of lenses),passing the patterned beam through the immersion liquid, and exposing aportion of the substrate with the patterned beam. In an embodiment, thesubstrate is a semiconductor substrate, e.g. a semiconductor wafer. Inan embodiment, the semiconductor substrate material is selected from thegroup consisting of Si, SiGe, SiGeC, SiC, Ge, GaAs, InP, and InAs. In anembodiment, the semiconductor substrate is a III/V semiconductorcompound. In an embodiment, the semiconductor substrate is a siliconsubstrate. In an embodiment, the substrate is a glass substrate. In anembodiment, the substrate is a ceramic substrate. In an embodiment, thesubstrate is an organic substrate, e.g. a plastic substrate. In anembodiment, the substrate is a photosensitive substrate, e.g. by havingcoated the substrate with a layer of resist.

In an embodiment, a device manufacturing process is provided comprising:

(i) patterning a beam of radiation;

(ii) passing the patterned beam of radiation through an aqueous liquid,said aqueous liquid comprising ions formed by a component having a vaporpressure greater than 0.I kPa;

(iii) exposing a photosensitive substrate to the patterned beam ofradiation.

Also, in an embodiment, a process is provided comprising:

(i) patterning a beam of radiation;

(ii) passing the patterned beam of radiation through a liquid comprisingan acid or a base, said acid or base having a vapor pressure exceedingthe vapor pressure of said liquid;

(ii) exposing a photosensitive substrate to radiation, wherein saidradiation has passed through said aqueous liquid comprising saidcomponent prior to reaching said photosensitive substrate.

In an embodiment, the process is a lithography process, such as animmersion lithography process. An example of an apparatus for carryingout an immersion lithography process is shown in FIG. 1. The apparatusdepicted in FIG. 1 comprises:

an illumination system (illuminator) IL configured to condition aradiation beam PB (e.g. UV radiation or DUV radiation);

a support structure (e.g. a mask table) MT constructed to support apatterning device MA and connected to a first positioner PM configuredto accurately position the patterning device in accordance with certainparameters. The support structure supports, i.e. bears the weight of,the patterning device. It holds the patterning device in a manner thatdepends on the orientation of the patterning device, the design of thelithographic apparatus, and other conditions, such as for examplewhether or not the patterning device is held in a vacuum environment.The support structure can use mechanical, vacuum, electrostatic or otherclamping techniques to hold the patterning device. The support structuremay be a frame or a table, for example, which may be fixed or movable asrequired. The support structure may ensure that the patterning device isat a desired position, for example with respect to the projectionsystem. The term “patterning device” used herein should be broadlyinterpreted as referring to any device that can be used to impart aradiation beam with a pattern in its cross-section such as to create apattern in a target portion of the substrate. It should be noted thatthe pattern imparted to the radiation beam may not exactly correspond tothe desired pattern in the target portion of the substrate, for exampleif the pattern includes phase-shifting features or so called assistfeatures. Generally, the pattern imparted to the radiation beam willcorrespond to a particular functional layer in a device being created inthe target portion, such as an integrated circuit. The patterning devicemay be transmissive or reflective. Examples of patterning devicesinclude masks and arrays of individually programmable elements (e.g.,programmable mirror arrays or programmable LCD panels). Masks are wellknown in lithography, and include mask types such as binary, alternatingphase-shift, and attenuated phase-shift, as well as various hybrid masktypes. An example of a programmable mirror array employs a matrixarrangement of small mirrors, which can be individually tilted so as toreflect an incoming radiation beam in different directions. The tiltedmirrors impart a pattern in a radiation beam which is reflected by themirror matrix.

a substrate table (e.g. a wafer table) WT constructed to hold asubstrate (e.g. a resist-coated wafer) W and connected to a secondpositioner PW configured to accurately position the substrate inaccordance with certain parameters. In an embodiment, the wafer tablecomprises one or more sensors (not shown), e.g. an image sensor (forinstance a transmission image sensor), a dose sensor, and/or anaberration sensor. In an embodiment, one or more of the sensors compriseone or more metals, e.g. chromium. In an embodiment, one or more of thesensors are coated, e.g. with titanium nitride.

a projection system (e.g., a refractive projection lens system) PLconfigured to project a pattern imparted to the radiation beam PB bypatterning device MA onto a target portion C (e.g. comprising one ormore dies) of the substrate W.

The illumination system may include various types of optical components,such as refractive, reflective, magnetic, electromagnetic, electrostaticor other types of optical components, or any combination thereof, fordirecting, shaping, or controlling radiation. The term “projectionsystem” used herein should be broadly interpreted as encompassing anytype of projection system, including refractive, reflective,catadioptric, magnetic, electromagnetic and electrostatic opticalsystems, or any combination thereof, as appropriate for the exposureradiation being used, or for other factors such as the use of theimmersion liquid or the use of a vacuum. In an embodiment, theprojection system includes an array of lenses. In an embodiment, theapparatus comprises an array of projection systems, e.g. to increasethroughput.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables (and/or two or more mask tables). In such“multiple stage” machines the additional tables may be used in parallel,or preparatory steps may be carried out on one or more tables while oneor more other tables are being used for exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source and the lithographic apparatus may beseparate entities, for example when the source is an excimer laser. Insuch cases, the source is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDcomprising, for example, suitable directing mirrors and/or a beamexpander. In other cases the source may be an integral part of thelithographic apparatus, for example when the source is a mercury lamp.The source SO and the illuminator IL, together with the beam deliverysystem BD if required, may be referred to as a radiation system. In anembodiment, the radiation provided by radiation source SO has awavelength of at least 50 nm, e.g. at least 1 OOnm, at least 150 nm, atleast 175 nm, at least 200 nm, at least 225 nm, at least 275 nm, atleast 325 nm, at least 350 nm, or at least 360 nm. In an embodiment, theradiation provided by radiation source SO has a wavelength of at most450 nm, e.g. at most 425 nm, at most 375 ntn, at most 360 nm, at most325 nm, at most 275 nm, at most 250 nm, at most 225 nm, at most 200 nni,or at most 175 nm. In an embodiment, the radiation has a wavelength of365 nm, 355 nm, 248 nm, or 193 nm.

The illuminator IL may comprise an adjuster AD for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator can be adjusted. In addition, the illuminator IL maycomprise various other components, such as an integrator IN and acondenser CO. The illuminator may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross-section.

The radiation beam PB is incident on the patterning device MA, which isheld by the support structure MT, and is patterned by the patterningdevice. Having traversed the patterning device, the radiation beam PBpasses through the projection system PL, which focuses the beam onto atarget portion C of the substrate W. An immersion hood IH, which isdescribed further below, supplies immersion liquid to a space betweenthe final element of the projection system PL and the substrate W. In anembodiment, the substrate table WT and immersion hood IH are connectedto a voltage generator V (e.g., a battery) that is capable of providinga voltage difference between the substrate table WT and the immersionhood IH (e.g. between a sensor plate of substrate table WT and theimmersion hood IH).

With the aid of the second positioner PW and position sensor IF (e.g. aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g. so as to positiondifferent target portions C in the path of the radiation beam PB.Similarly, the first positioner PM and another position sensor (which isnot explicitly depicted in FIG. 1) can be used to accurately positionthe patterning device MA with respect to the path of the radiation beamPB, e.g. after mechanical retrieval from a mask library, or during ascan. In general, movement of the support structure MT may be realizedwith the aid of a long-stroke module (coarse positioning) and ashort-stroke module (fine positioning), which form part of the firstpositioner PM. Similarly, movement of the substrate table WT may berealized using a long-stroke module and a short-stroke module, whichform part of the second positioner PW. In the case of a stepper (asopposed to a scanner) the support structure MT may be connected to ashort-stroke actuator only, or may be fixed. Patterning device MA andsubstrate W may be aligned using alignment marks M1, M2 and substratealignment marks P1, P2. Although the substrate alignment marks asillustrated occupy dedicated target portions, they may be located inspaces between target portions (these are known as scribe-lane alignmentmarks).

Similarly, in situations in which more than one die is provided by thepatterning device MA, the alignment marks may be located between thedies.

The depicted apparatus could be used in at least one of the followingmodes:

1. hi step mode, the support structure MT and the substrate table WT arekept essentially stationary, while an entire pattern imparted to theradiation beam is projected onto a target portion C at one time (i.e. asingle static exposure). The substrate table WT is then shifted in the Xand/or Y direction so that a different target portion C can be exposed.In step mode, the maximum size of the exposure field limits the size ofthe target portion C imaged in a single static exposure.

2. In scan mode, the support structure MT and the substrate table WT arescanned synchronously while a pattern imparted to the radiation beam isprojected onto a target portion C (i.e. a single dynamic exposure). Thevelocity and direction of the substrate table WT relative to the supportstructure MT may be determined by the (de-)magnification and imagereversal characteristics of the projection system PL. In scan mode, themaximum size of the exposure field limits the width (in the non-scanningdirection) of the target portion in a single dynamic exposure, whereasthe length of the scanning motion determines the height (in the scanningdirection) of the target portion.

3. In another mode, the support structure MT is kept essentiallystationary holding a programmable patterning device, and the substratetable WT is moved or scanned while a pattern imparted to the radiationbeam is projected onto a target portion C. In this mode, generally apulsed radiation source is employed and the programmable patterningdevice is updated as required after each movement of the substrate tableWT or in between successive radiation pulses during a scan. This mode ofoperation can be readily applied to maskless lithography that utilizesprogrammable patterning device, such as a programmable mirror array of atype as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

FIG. 2 illustrates an embodiment of an immersion hood IH. Immersion Hood10 forms a contactless seal to the substrate around the image field ofthe projection system so that immersion liquid 11 is confined to fill aspace between the substrate surface and the final element of theprojection system. The reservoir is formed by a seal member 12positioned below and surrounding the final element of the projectionsystem PL. Immersion liquid 11 is brought into the space below theprojection system and within the seal member 12. The seal member 12extends a little above the final element of the projection system andthe liquid level rises above the final element so that a buffer ofliquid is provided. The seal member 12 has an inner periphery that atthe upper end, in an embodiment, closely conforms to the shape of theprojection system or the final element thereof and may, e.g., be round.At the bottom, the inner periphery closely conforms to the shape of theimage field, e.g., rectangular though this need not be the case.

The immersion liquid 11 is confined in the immersion hood 10 by a gasseal 16 between the bottom of the seal member 12 and the surface of thesubstrate W. The gas seal is formed by gas, e.g. air or synthetic airbut, in an embodiment, N₂ or an inert gas, provided under pressure viainlet 15 to the gap between seal member 12 and substrate and extractedvia first outlet 14. The overpressure on the gas inlet 15, vacuum levelon the first outlet 14 and geometry of the gap are arranged so thatthere is a high-velocity gas flow inwards that confines the liquid.

Products

Some examples of devices that can be created with the present processand system include, e.g., micro electromechanical systems (“MEMS”), thinfilm heads, integrated passive components, image sensors, integratedcircuits (“ICs”)—including, e.g., power ICs, analog ICs, and discreteICs—, and liquid crystal displays.

Having described specific embodiments of the invention, it will beunderstood that many modifications thereof will readily appear or may besuggested to those skilled in the art, and it is intended therefore thatthis invention is limited only by the spirit and scope of the followingclaims.

1. A device manufacturing process comprising: (i) adding a component toa liquid, said component having a vapor pressure greater than 0.1 kPa;(ii) exposing a photosensitive substrate to radiation, wherein saidradiation has passed through said aqueous liquid comprising saidcomponent prior to reaching said photosensitive substrate; wherein saidadding of said component increases the ion concentration in said liquid.2. The process of claim 1, wherein said component has a vapor pressuregreater than water.
 3. The process of claim 1, wherein said componentlowers the pH of said liquid.
 4. The process of claim 1, wherein saidcomponent raises the pH of said liquid.
 5. The process of claim 1,wherein said component has a vapor pressure of at least 1 kPa.
 6. Theprocess of claim 1, wherein said liquid comprises, relative to the totalweight of said liquid, at least 90 wt % of water.
 7. The process ofclaim 1, wherein said liquid comprises, relative to the total weight ofsaid liquid, at least 99.9 wt % of water.
 8. The process of claim 1,wherein said component is a gas at 20° C. and atmospheric pressure. 9.The process of claim 1, wherein said liquid comprising said componenthas a pH in the range of 4.5-6.0.
 10. The process of claim 1, whereinsaid component is carbon dioxide or ammonia.
 11. The process of claim 1,wherein said liquid comprising said component is essentially absentcomponents having a vapor pressure lower than 2.0 kPa.
 12. The processof claim 1, wherein said substrate is a semiconductor wafer coated witha layer of resist.
 13. The process of claim 1, wherein said radiation isUV radiation having a wavelength in the range of 175 nm-375 nm.
 14. Theprocess of claim 1, further comprising passing said radiation through anarray of lenses prior to passing said radiation through said liquidcomprising said component.
 15. The process of claim 1, furthercomprising patterning said radiation prior to passing said radiationthrough said liquid comprising said component.
 16. The process of claim15, wherein said patterning is effected with a mask or an array ofindividually programmable elements.
 17. The process of claim 1, whereinsaid photosensitive substrate rests on a substrate table during saidexposing, said substrate table comprising a sensor, said sensorcomprising titanium nitride and/or a metal.
 18. The process of claim 1,comprising adding at least 2 components having a vapor pressure of atleast 0.1 kPa to said liquid.
 19. A device manufactured with the processof claim
 1. 20. The device of claim 19, wherein said device is anintegrated circuit.
 21. A device manufacturing process comprising: (i)adding an acid or base to a liquid, said acid or base having a vaporpressure of at least 0.1 kPa; (ii) exposing a photosensitive substrateto radiation, wherein said radiation has passed through said liquidcomprising said component prior to reaching said photosensitivesubstrate.
 22. The process of claim 21, comprising adding an acid tosaid liquid.
 23. The process of claim 21, comprising adding a base tosaid liquid.
 24. A device manufacturing process comprising: (i)patterning a beam of radiation; (ii) passing the patterned beam ofradiation through a liquid, said liquid comprising ions formed by acomponent having a vapor pressure greater than 0.1 kPa, the conductivityof said aqueous liquid being at least 0.25 μS/cm (as determined at 25°C.); and (iii) exposing a photosensitive substrate to the patterned beamof radiation.
 25. An immersion lithography system comprising: (i) animmersion lithography exposure apparatus; and (ii) an immersion liquidhaving an electric conductivity in the range of 1.3-100 μS/cm (asdetermined at 25° C.).
 26. The system of claim 25, wherein saidconductivity is at least 5 μS/cm.
 27. The system of claim 25, whereinsaid conductivity is at most 50 μS/cm.
 28. The system of claim 25,wherein said conductivity is in the range of 2-10 μS/cm.
 29. The systemof claim 25, wherein said immersion liquid is formed by adding a salt, abase, or an acid to an aqueous liquid.
 30. The system of claim 25,wherein said immersion liquid comprises carbon dioxide.
 31. The systemof claim 25, wherein said immersion liquid has a pH below 6.0.
 32. Thesystem of claim 25, wherein said immersion lithography exposureapparatus includes a substrate table having a sensor comprising chromiumand/or titanium nitride.
 33. The system of claim 25, wherein saidconductivity is caused at least in part by a component having a vaporpressure greater than 5 kPa.
 34. A lithography apparatus having avoltage generator functionally connected to a first part of alithography apparatus, said first part being a substrate table, andfunctionally connected to a second part of the lithography apparatus,said voltage generator being capable of establishing a voltagedifference between said first part and said second part.
 35. Theapparatus of claim 34, wherein said apparatus is an immersionlithography apparatus and said second part is an immersion hood.